Japanese Patent Publication No. 3,655,627 discloses an apparatus for successively making plastic bags each of which includes a panel portion and side gusset portions. In the apparatus, first and second webs of panel material are superposed with each other and fed longitudinally thereof. A web of side gusset material is folded into halves and supplied to the first web′ of panel material to extend widthwise of the first web of panel material before the first and second webs of panel material are superposed with each other. The web of side gusset material is crosscut into a length corresponding to the width of the first and second webs of panel material. The web of side gusset material is then interposed between the first and second webs of panel material after the first and second webs of panel material are superposed with each other.
The apparatus includes a longitudinal seal device by which the first and second webs of panel material are heat sealed with each other longitudinally thereof after being superposed with each other. The apparatus further includes a cross seal device by which the first and second webs of panel material and the web of side gusset material are heat sealed with each other widthwise of the first and second webs of panel material after the first and second webs of panel material are superposed with each other. The apparatus further includes a cutter by which the first and second webs of panel material are crosscut widthwise thereof after being heat sealed. The panel portion is formed of the first and second webs of panel material. The side gusset portion is formed of the web of side gusset material. The apparatus can successively make plastic bags at high speed, resulting in high performance.
On the other hand, Japanese Laid-Open Patent Publication No. 347,788 of 2002 discloses a plastic bag including not only the panel portion and the side gusset portions but also a fastener portion. The panel portion is formed of first and second sheets of panel material. The side gusset portion is formed of a sheet of side gusset material.
The fastener portion extends along the top edge of plastic bag. The fastener portion has a specific structure, in which a first body of fastener material is joined to the first sheet of panel material while a second body of fastener material is joined to the second sheet of panel material within the plastic bag. A third body of fastener material is joined to the sheet of side gusset material within the plastic bag, the fastener portion being formed of the first, second and third bodies of fastener material. The first and second bodies of fastener material are meshing engaged with each other and with the third body of fastener material. The plastic bag can therefore be closed by the first, second and third bodies of fastener material. The first, second and third bodies of fastener material comprise parts of hook and loop touch fastener portion. The plastic bag would be used for various purposes to be high in utility, regardless of a problem of airtightness of hook and loop touch fastener portion.
It is therefore required to improve the apparatus of Japanese Patent No. 3,655,627 to successively make plastic bags each of which has the same structure as that of Japanese Laid-Open Patent Publication No. 347,788 of 2002.